1. Field of Invention
This invention relates to a fluid ejection system.
2. Description of Related Art
Ink jet printers have at least one printhead that directs droplets of ink towards a recording medium. Within the printhead, the ink may be contained in a plurality of channels. Energy pulses are used to expel the droplets of ink, as required, from orifices at the ends of the channels.
In a thermal ink jet printer, the energy pulses are usually produced by resistors. Each resistor is located in a respective one of the channels, and is individually addressable by current pulses to heat and vaporize ink in the channels. As a vapor bubble grows in any one of the channels, ink bulges from the channel orifice until the current pulse has ceased and the bubble begins to collapse. At that stage, the ink within the channel retracts and separates from the bulging ink to form a droplet moving in a direction away from the channel and towards the recording medium. The channel is then re-filled by capillary action, which in turn draws ink from a supply container. Operation of a thermal ink jet printer is described in, for example, U.S. Pat. No. 4,849,774.
A carriage-type thermal ink jet printer is described in U.S. Pat. No. 4,638,337. That printer has a plurality of printheads, each with its own ink tank cartridge, mounted on a reciprocating carriage. The channel orifices in each printhead are aligned perpendicular to the line of movement of the carriage. A swath of information is printed on the stationary recording medium as the carriage is moved in one direction. The recording medium is then stepped, perpendicular to the line of carriage movement, by a distance equal to the width of the printed swath. The carriage is then moved in the reverse direction to print another swath of information.
As described above, inkjet printing systems usually use a single printhead, or array of colored printheads, that print a swath of information. Thus, the ink jet printer""s productivity is limited to the size of the printheads used. During printing, the printheads print a swath of information. In order to increase productivity after printing a swath of information, the printheads move a full swath width relative to the printed swath of information. Thereafter, the printheads print an additional swath of information. However, the quality of printing when using this process is reduced as the opportunity to place ink drops in a given location is limited to one pass of the printhead. Another problem occurs in that stitch errors occur between each swath as the printhead fails to align with the previous swath.
One technique for dealing with this problem is to overlap adjacently produced swaths. However, overlapping the swaths reduces the productivity of the ink jet printer system, as the printhead moves in smaller increments based on the amount of desired overlap. Another technique used to improve productivity adds additional printheads by staggering the multiple printheads together or placing the additional printheads in line with the first printhead along the lines of carriage movement. However, this increases the scanning distance required to print each swath, which has a negative affect on system productivity.
This invention provides multiple pass printing with relatively small printheads and with high productivity.
This invention separately provides a fluid ejection system that can efficiently mask image quality defects that occur at the stitch point between swaths formed by individual printheads.
This invention separately provides a fluid ejection system that can advance a full swath distance between printhead scans.
In various exemplary embodiments of a fluid ejection system and methods according to this invention, the fluid ejection system includes a printhead system with at least two printheads. One printhead is located adjacent to a second printhead such that the printhead system can advance a full swath distance between each scan.
In various exemplary embodiments, a first printhead is placed less than one swath distance away from a second printhead. In other various exemplary embodiments, the first printhead is placed more than one swath distance away from the second printhead.
In various exemplary embodiments, the distance between the swaths printed by the first and second printheads is less than the swath width of at least the second printhead. In other various exemplary embodiments, the distance between the swaths printed by the first and second printheads is more than the swath width of at least the second printhead.
These and other features and advantages of this invention are described in or are apparent from the detailed description of various exemplary embodiments of the systems and methods according to this invention.